The cooling of the reciprocating pistons of an internal combustion engine with cooling fluids, including oil is well known. The use of oil can be quite effective in reducing piston temperature and may also lubricate the piston as well. However, the various devices currently available for directing oil or other cooling fluids toward the piston do not reliably achieve optimum cooling. Unless the device used to direct the oil to the piston can be precisely positioned so that the cooling oil is sprayed or otherwise applied substantially uniformly to all of the piston surfaces to be cooled, localized "hot spots" may be created, and cracking of the piston could result from the temperature differentials thus produced.
This problem may be particularly pronounced when the piston to be cooled is a gallery type or articulated piston with a central cavity that is open at the end toward the connecting rod. The various internal piston structures and the connecting rod are likely to interfere with the application of cooling oil to the interior of the piston, particularly while the piston is reciprocating in the cylinder during engine operation.
The application of cooling oil to the piston interior has been accomplished in different ways by the prior art. For example, in Johnson, Jr. et al. U.S. Pat. No. 4,206,726, a piston cooling nozzle is mounted through a hole in the engine block. Several retainer plates are used to hold the nozzle in place on the engine block and to ensure proper orientation of the nozzle jets. The nozzle shaft intersects an oil gallery in the engine block to provide oil under pressure to the nozzle jets. This arrangement directs cooling oil to the piston interior and can be aligned to provide a cooling oil spray to this part of the piston to cool it during engine operation. However, the piston cooling nozzle and retainer plates described in Pat. No. 4,206,726 must be installed, adjusted and removed from the interior of the engine block, which involves removing the engine side cover. Consequently, there is no way to determine whether the nozzle is correctly aligned to direct an optimal spray of cooling oil to the piston interior without removing the engine side cover. The installation, maintenance and replacement of such a piston cooling nozzle, therefore, is both labor intensive and costly.
The prior art also discloses other piston cooling nozzles and similar devices. U.S. Pat. Nos. 3,709,109 to Howe; 4,067,307 to Hofle et al.; and 4,508,065 to Suchdev are illustrative of the prior art relating to such piston cooling structures. The selectively rotatable piston nozzle disclosed in Pat. No. 3,709,109 can be mounted to selectively direct a spray of cooling oil against a desired portion of the piston. However, this piston nozzle is installed inside the engine block during manufacture of the engine. Adjustment of the nozzle after installation to insure that oil is being sprayed to the piston at a location and in a manner that will achieve optimal cooling is extremely difficult with this design.
Suchdev Pat. No. 4,508,065 discloses a piston cooling delivery tube including a bracket attached to the cylinder liner in a predetermined fixed position. The tube is prealigned to direct the cooling oil to a particular location. As a result, if the tube becomes misaligned so that the cooling spray is not directed to the optimum location, correction of the adjustment can only be achieved by disassembling the engine block.
There is no disclosure in Pat. No. 4,067,307 of how the piston cooling nozzle described in that patent is mounted on the engine block or whether it may be adjusted to direct a spray of cooling oil toward a piston to achieve optimal cooling.
The piston cooling nozzles of the prior art are not as effective as desired at providing a precisely directed spray of cooling oil to achieve optimal cooling of an articulated or gallery piston in a high horsepower engine. While these nozzles may perform an adequate cooling function for some types of pistons and engines, their long-term reliability is difficult to insure. The prior art piston nozzles that are targeted to direct cooling oil to a specific area of the piston and, therefore, can provide optimum cooling even of articulated pistons in high horsepower engines are mounted from the inside of the engine block. Consequently, if one of these targeted piston nozzles becomes misaligned so that the cooling oil spray is not directed to the desired location, the only way to correct the misalignment is to disassemble at least a portion of the engine block. None of the targeted piston cooling nozzles of the prior art is readily accessible from the outside of the engine block. As a result, the cost of installing, maintaining, and replacing such devices can be quite high.
Piston cooling devices that can be mounted from the outside of the engine block and thus avoid the costly and time consuming maintenance problems described above are available. The nozzle disclosed in Pat. No. 3,709,109 is an example. However, this nozzle is not targeted or aligned to insure that a spray of cooling oil or fluid will be directed to a specific area of the interior of a gallery type piston to produce optimum piston cooling in a high horsepower internal combustion engine. Further, because the piston cooling nozzle of Pat. No. 3,709,109 is rotatable to move it from an actuated to a deactuated condition, it may rotate away from its optimal actuated position so that cooling oil is not directed to the proper location. Such mis-direction may go undetected for a sufficiently long period that uneven cooling of the piston and its associated problems occur.
The prior art, therefore, fails to provide a precisely targeted piston cooling assembly that may be easily installed, serviced and replaced from outside of the engine block to reliably insure the direction by the nozzle of a spray of cooling oil to a specific location in an articulated or gallery piston that will achieve optimum piston cooling in a high horsepower engine.